MOULDS. 169 



by means of transverse walls into short cylindrical pieces, so 

 that finally the whole plant is transformed into numbers of 

 " Oidia," each one of which is capable of giving rise to a 

 new individual. 



The reproductive bodies are termed spores. Of these, the 

 simplest kind are the conidia, which are formed by constriction 

 from one or more of the mycelial hyphse, termed the conidio- 

 phores. This constriction may take place in two ways. In 

 the first case, under the conidium first formed at the end of the 

 thread a new growth develops, the new piece swells out and 

 forms a new conidium, and so the development continues, 

 the successive spores being produced basipetally i.e., towards 

 the base of the thread. This is the method of spore-formation 

 in Penicillium (see Fig. 33). In the second case, the spore 

 first formed at the end of the thread expands at its upper 

 end, and is constricted to form a new conidium, and the 

 development proceeds in this way from the base of the thread 

 upwards (basifugal). These conidia may, however, also 

 develop spores sideways. This development is similar to 

 the budding of yeast cells. It has been observed in Clado- 

 sporium. The conidiophore may be branched, or may assume 

 a still more complex structure. Reference to Fig. 33, for 

 instance, will show the condition in Penicillium, where the 

 numerous and minute conidia are arranged in long chains, 

 each at the tip of an individual branch. An altogether different 

 kind of spore-formation is that which results in the production 

 of zygospores, such as are met with in Mucor, and described 

 in detail further on. The remarkable feature of this kind of 

 spore-formation is that it is brought about by the fusing 

 together of two cells, between which there would appear to 

 exist a definite distinction of sex. In contrast to these, we 

 find other spores produced in the interior of certain cells. 

 Here, again, Mucor serves us with an example (Fig. 35), where 

 each mycelium carries a sporangium in the interior of which 

 a large number of oval spores are formed round a column 

 (columella), which are liberated by the rupture of the wall. 



Quite a different class of internal spore is met with in 

 such forms as Aspergillus (Fig. 34). Here a small and definite 

 number of spores are produced in a tubular cell (ascus). In 



